/*
 * Copyright 2002-2019 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.web.reactive.function.server;

import org.reactivestreams.Publisher;
import org.springframework.core.ParameterizedTypeReference;
import org.springframework.http.CacheControl;
import org.springframework.http.HttpHeaders;
import org.springframework.http.HttpMethod;
import org.springframework.http.HttpStatus;
import org.springframework.http.MediaType;
import org.springframework.http.ResponseCookie;
import org.springframework.http.codec.json.Jackson2CodecSupport;
import org.springframework.http.server.reactive.ServerHttpResponse;
import org.springframework.util.MultiValueMap;
import org.springframework.web.reactive.function.BodyInserter;
import org.springframework.web.reactive.function.BodyInserters;
import reactor.core.publisher.Mono;

import java.net.URI;
import java.time.Instant;
import java.time.ZonedDateTime;
import java.util.Map;
import java.util.Set;
import java.util.function.Consumer;

/**
 * Entity-specific subtype of {@link ServerResponse} that exposes entity data.
 *
 * @param <T> the entity type
 * @author Arjen Poutsma
 * @author Juergen Hoeller
 * @since 5.0
 */
public interface EntityResponse<T> extends ServerResponse {

    /**
     * Create a builder with the given object.
     *
     * @param t   the object that represents the body of the response
     * @param <T> the type of the elements contained in the publisher
     * @return the created builder
     */
    static <T> Builder<T> fromObject(T t) {
        return new DefaultEntityResponseBuilder<>(t, BodyInserters.fromObject(t));
    }

    /**
     * Create a builder with the given publisher.
     *
     * @param publisher    the publisher that represents the body of the response
     * @param elementClass the class of elements contained in the publisher
     * @param <T>          the type of the elements contained in the publisher
     * @param <P>          the type of the {@code Publisher}
     * @return the created builder
     */
    static <T, P extends Publisher<T>> Builder<P> fromPublisher(P publisher, Class<T> elementClass) {
        return new DefaultEntityResponseBuilder<>(publisher,
                BodyInserters.fromPublisher(publisher, elementClass));
    }


    // Static builder methods

    /**
     * Create a builder with the given publisher.
     *
     * @param publisher     the publisher that represents the body of the response
     * @param typeReference the type of elements contained in the publisher
     * @param <T>           the type of the elements contained in the publisher
     * @param <P>           the type of the {@code Publisher}
     * @return the created builder
     */
    static <T, P extends Publisher<T>> Builder<P> fromPublisher(P publisher,
                                                                ParameterizedTypeReference<T> typeReference) {

        return new DefaultEntityResponseBuilder<>(publisher,
                BodyInserters.fromPublisher(publisher, typeReference));
    }

    /**
     * Return the entity that makes up this response.
     */
    T entity();

    /**
     * Return the {@code BodyInserter} that writes the entity to the output stream.
     */
    BodyInserter<T, ? super ServerHttpResponse> inserter();


    /**
     * Defines a builder for {@code EntityResponse}.
     *
     * @param <T> a self reference to the builder type
     */
    interface Builder<T> {

        /**
         * Add the given header value(s) under the given name.
         *
         * @param headerName   the header name
         * @param headerValues the header value(s)
         * @return this builder
         * @see HttpHeaders#add(String, String)
         */
        Builder<T> header(String headerName, String... headerValues);

        /**
         * Copy the given headers into the entity's headers map.
         *
         * @param headers the existing HttpHeaders to copy from
         * @return this builder
         * @see HttpHeaders#add(String, String)
         */
        Builder<T> headers(HttpHeaders headers);

        /**
         * Set the HTTP status.
         *
         * @param status the response status
         * @return this builder
         */
        Builder<T> status(HttpStatus status);

        /**
         * Set the HTTP status.
         *
         * @param status the response status
         * @return this builder
         * @since 5.0.3
         */
        Builder<T> status(int status);

        /**
         * Add the given cookie to the response.
         *
         * @param cookie the cookie to add
         * @return this builder
         */
        Builder<T> cookie(ResponseCookie cookie);

        /**
         * Manipulate this response's cookies with the given consumer. The
         * cookies provided to the consumer are "live", so that the consumer can be used to
         * {@linkplain MultiValueMap#set(Object, Object) overwrite} existing cookies,
         * {@linkplain MultiValueMap#remove(Object) remove} cookies, or use any of the other
         * {@link MultiValueMap} methods.
         *
         * @param cookiesConsumer a function that consumes the cookies
         * @return this builder
         */
        Builder<T> cookies(Consumer<MultiValueMap<String, ResponseCookie>> cookiesConsumer);

        /**
         * Set the set of allowed {@link HttpMethod HTTP methods}, as specified
         * by the {@code Allow} header.
         *
         * @param allowedMethods the allowed methods
         * @return this builder
         * @see HttpHeaders#setAllow(Set)
         */
        Builder<T> allow(HttpMethod... allowedMethods);

        /**
         * Set the set of allowed {@link HttpMethod HTTP methods}, as specified
         * by the {@code Allow} header.
         *
         * @param allowedMethods the allowed methods
         * @return this builder
         * @see HttpHeaders#setAllow(Set)
         */
        Builder<T> allow(Set<HttpMethod> allowedMethods);

        /**
         * Set the entity tag of the body, as specified by the {@code ETag} header.
         *
         * @param etag the new entity tag
         * @return this builder
         * @see HttpHeaders#setETag(String)
         */
        Builder<T> eTag(String etag);

        /**
         * Set the time the resource was last changed, as specified by the
         * {@code Last-Modified} header.
         * <p>The date should be specified as the number of milliseconds since
         * January 1, 1970 GMT.
         *
         * @param lastModified the last modified date
         * @return this builder
         * @see HttpHeaders#setLastModified(long)
         */
        Builder<T> lastModified(ZonedDateTime lastModified);

        /**
         * Set the time the resource was last changed, as specified by the
         * {@code Last-Modified} header.
         * <p>The date should be specified as the number of milliseconds since
         * January 1, 1970 GMT.
         *
         * @param lastModified the last modified date
         * @return this builder
         * @see HttpHeaders#setLastModified(long)
         * @since 5.1.4
         */
        Builder<T> lastModified(Instant lastModified);

        /**
         * Set the location of a resource, as specified by the {@code Location} header.
         *
         * @param location the location
         * @return this builder
         * @see HttpHeaders#setLocation(URI)
         */
        Builder<T> location(URI location);

        /**
         * Set the caching directives for the resource, as specified by the HTTP 1.1
         * {@code Cache-Control} header.
         * <p>A {@code CacheControl} instance can be built like
         * {@code CacheControl.maxAge(3600).cachePublic().noTransform()}.
         *
         * @param cacheControl a builder for cache-related HTTP response headers
         * @return this builder
         * @see <a href="https://tools.ietf.org/html/rfc7234#section-5.2">RFC-7234 Section 5.2</a>
         */
        Builder<T> cacheControl(CacheControl cacheControl);

        /**
         * Configure one or more request header names (e.g. "Accept-Language") to
         * add to the "Vary" response header to inform clients that the response is
         * subject to content negotiation and variances based on the value of the
         * given request headers. The configured request header names are added only
         * if not already present in the response "Vary" header.
         *
         * @param requestHeaders request header names
         * @return this builder
         */
        Builder<T> varyBy(String... requestHeaders);

        /**
         * Set the length of the body in bytes, as specified by the
         * {@code Content-Length} header.
         *
         * @param contentLength the content length
         * @return this builder
         * @see HttpHeaders#setContentLength(long)
         */
        Builder<T> contentLength(long contentLength);

        /**
         * Set the {@linkplain MediaType media type} of the body, as specified by the
         * {@code Content-Type} header.
         *
         * @param contentType the content type
         * @return this builder
         * @see HttpHeaders#setContentType(MediaType)
         */
        Builder<T> contentType(MediaType contentType);

        /**
         * Add a serialization hint like {@link Jackson2CodecSupport#JSON_VIEW_HINT} to
         * customize how the body will be serialized.
         *
         * @param key   the hint key
         * @param value the hint value
         */
        Builder<T> hint(String key, Object value);

        /**
         * Manipulate serialization hint with the given consumer.
         *
         * @param hintsConsumer a function that consumes the hints
         * @return this builder
         * @since 5.1.6
         */
        Builder<T> hints(Consumer<Map<String, Object>> hintsConsumer);

        /**
         * Build the response.
         *
         * @return the built response
         */
        Mono<EntityResponse<T>> build();
    }

}
